scholarly journals VHF volume-imaging radar observation of aspect-sensitive scatterers tilted in mountain waves above a convective boundary layer

2005 ◽  
Vol 23 (4) ◽  
pp. 1139-1145 ◽  
Author(s):  
R. M. Worthington
Keyword(s):  
Gravity Waves ◽  
Air Flow ◽  
Horizontal Wind ◽  
Convective Boundary ◽  
Mountain Waves ◽  
Imaging Radar ◽  
Mu Radar ◽  
Volume Imaging ◽  
Wind Measurements ◽  
To Receive

Abstract. Thin stable atmospheric layers cause VHF radars to receive increased echo power from near zenith. Layers can be tilted from horizontal, for instance by gravity waves, and the direction of VHF "glinting" is measurable by spatial domain interferometry or many-beam Doppler beam swinging (DBS). This paper uses the Middle and Upper atmosphere (MU) radar, Shigaraki, Japan as a volume-imaging radar with 64-beam DBS, to show tilting of layers and air flow in mountain waves. Tilt of aspect-sensitive echo power from horizontal is nearly parallel to air flow, as assumed in earlier measurements of mountain-wave alignment. Vertical-wind measurements are self-consistent from different beam zenith angles, despite the combined effects of aspect sensitivity and horizontal-wind gradients.

scholarly journals Derivation of gravity wave intrinsic parameters and vertical wavelength using a single scanning OH(3-1) airglow spectrometer

2018 ◽  
Vol 11 (5) ◽  
pp. 2937-2947 ◽  
Author(s):  
Sabine Wüst ◽  
Thomas Offenwanger ◽  
Carsten Schmidt ◽  
Michael Bittner ◽  
Christoph Jacobi ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Spatial Information ◽  
Rotational Transition ◽  
Horizontal Wind ◽  
Vertical Temperature ◽  
Vertical Wavelength ◽  
Broadband Emission ◽  
Wind Measurements ◽  
First Time

Abstract. For the first time, we present an approach to derive zonal, meridional, and vertical wavelengths as well as periods of gravity waves based on only one OH* spectrometer, addressing one vibrational-rotational transition. Knowledge of these parameters is a precondition for the calculation of further information, such as the wave group velocity vector. OH(3-1) spectrometer measurements allow the analysis of gravity wave ground-based periods but spatial information cannot necessarily be deduced. We use a scanning spectrometer and harmonic analysis to derive horizontal wavelengths at the mesopause altitude above Oberpfaffenhofen (48.09∘ N, 11.28∘ E), Germany for 22 nights in 2015. Based on the approximation of the dispersion relation for gravity waves of low and medium frequencies and additional horizontal wind information, we calculate vertical wavelengths. The mesopause wind measurements nearest to Oberpfaffenhofen are conducted at Collm (51.30∘ N, 13.02∘ E), Germany, ca. 380 km northeast of Oberpfaffenhofen, by a meteor radar. In order to compare our results, vertical temperature profiles of TIMED-SABER (thermosphere ionosphere mesosphere energetics dynamics, sounding of the atmosphere using broadband emission radiometry) overpasses are analysed with respect to the dominating vertical wavelength.

Multi-scale mountain waves observed with the ALIMA lidar during SOUTHTRAC-GW above the southern Andes

2021 ◽  
Author(s):  
Natalie Kaifler ◽  
Bernd Kaifler ◽  
Andreas Dörnbrack ◽  
Sonja Gisinger ◽  
Tyler Mixa ◽  
...  
Keyword(s):  
Wave Field ◽  
Gravity Wave ◽  
Gravity Waves ◽  
Momentum Flux ◽  
Middle Atmosphere ◽  
Airborne Lidar ◽  
Horizontal Wind ◽  
Measured Temperature ◽  
Southern Andes ◽  
Mountain Waves

<p>During the SOUTHTRAC-GW (Southern hemisphere Transport, Dynamics and Chemistry – Gravity Waves) field campaign, gravity waves above the Southern Andes mountains, the Drake passage and the Antarctic Peninsula were probed with airborne instruments onboard the HALO research aircraft. The Airborne Lidar for Middle Atmosphere research (ALIMA) detected particularly strong mountain waves in excess of 25 K amplitude in cross-mountain legs above the Southern Andes of research flight ST08 on 12 September 2019. The mountain waves propagated well into the mesosphere up to 65 km altitude with possible generation of smaller-scale secondary waves during wave breaking above 65 km. A superposition of mountain waves with horizontal wavelengths in the range 15-200 km and vertical wavelengths 7-24 km dominated the wave field between 18 and 65 km altitude. Vertical wavelengths predicted by the hydrostatic equation and horizontal wind from the European Center for Medium-Range Weather Forecasts’ Integrated Forecasting System are in good agreement with observed vertical wavelengths. We apply wavelet analysis to the measured temperature field along the flight track in order to identify and separate dominant scales, and estimate their relative contributions to the total gravity wave momentum flux as well as the local and zonal-mean gravity wave drag. Furthermore, we compare our observations to results obtained by Fourier ray analysis of the terrain of the Southern Andes. The Fourier model allows the investigation of the 3d-wave field and trapped waves which are not well sampled by the ALIMA instrument because of the relative alignment between the wave fronts and the flight track. These sampling biases are quantified from virtual flights through the model domain at multiple angles and taken into account in the estimation of the total momentum flux derived from ALIMA observations. The combination of high-resolution observations and model data reveals the significance of this and similar mountain wave events in the Southern Andes region for the atmospheric dynamics at ~60° S.</p>

scholarly journals Local Structure of the Convective Boundary Layer from a Volume-Imaging Radar

2000 ◽  
Vol 57 (14) ◽  
pp. 2281-2296 ◽  
Author(s):  
Brian D. Pollard ◽  
Samir Khanna ◽  
Stephen J. Frasier ◽  
John C. Wyngaard ◽  
Dennis W. Thomson ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Local Structure ◽  
Convective Boundary ◽  
Imaging Radar ◽  
Volume Imaging

scholarly journals Derivation of horizontal and vertical wavelengths using a scanning OH(3-1) airglow spectrometer

2017 ◽  
Author(s):  
Sabine Wüst ◽  
Thomas Offenwanger ◽  
Carsten Schmidt ◽  
Michael Bittner ◽  
Christoph Jacobi ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Spatial Information ◽  
Rotational Transition ◽  
Horizontal Wind ◽  
Vertical Temperature ◽  
Medium Frequency ◽  
Vertical Wavelength ◽  
Broadband Emission ◽  
Wind Measurements ◽  
First Time

Abstract. For the first time, we present an approach to derive zonal, meridional and vertical wavelengths as well as periods of gravity waves based on only one OH* spectrometer addressing one vibrational-rotational transition. Knowledge of these parameters is a precondition for the calculation of further information such as the wave group velocity vector. OH(3-1) spectrometer measurements allow the analysis of gravity wave periods, but spatial information cannot necessarily be deduced. We use a scanning spectrometer and the harmonic analysis to derive horizontal wavelengths at the mesopause above Oberpfaffenhofen (48.09 °N, 11.28 °E), Germany for 22 nights in 2015. Based on the approximation of the dispersion relation for gravity waves of low and medium frequency and additional horizontal wind information, we calculate vertical wavelengths afterwards. The mesopause wind measurements nearest to Oberpfaffenhofen are conducted at Collm (51.30 °N, 13.02 °E), Germany, ca. 380 km northeast of Oberfpaffenhofen by a meteor radar. In order to check our results, vertical temperature profiles of TIMED-SABER (Thermosphere Ionosphere Mesosphere Energetics Dynamics, Sounding of the Atmosphere using Broadband Emission Radiometry) overpasses are analysed with respect to the dominating vertical wavelength.

scholarly journals On strongly nonlinear gravity waves in a vertically sheared atmosphere

2020 ◽  
Vol 6 (1) ◽  
pp. 63-74
Author(s):  
Mark Schlutow ◽  
Georg S. Voelker
Keyword(s):  
Gravity Waves ◽  
Lower Layer ◽  
Vertical Shear ◽  
Horizontal Wind ◽  
Necessary Condition ◽  
Mean Flow ◽  
Individual Layer ◽  
Strongly Nonlinear ◽  
The Mean ◽  
The Stability

Abstract We investigate strongly nonlinear stationary gravity waves which experience refraction due to a thin vertical shear layer of horizontal background wind. The velocity amplitude of the waves is of the same order of magnitude as the background flow and hence the self-induced mean flow alters the modulation properties to leading order. In this theoretical study, we show that the stability of such a refracted wave depends on the classical modulation stability criterion for each individual layer, above and below the shearing. Additionally, the stability is conditioned by novel instability criteria providing bounds on the mean-flow horizontal wind and the amplitude of the wave. A necessary condition for instability is that the mean-flow horizontal wind in the upper layer is stronger than the wind in the lower layer.

Frequency of Mountain Waves Over Kanto Area Revealed by Imaging Observations of OH Airglow

2021 ◽  
Author(s):  
Satoshi Ishii ◽  
Yoshihiro Tomikawa ◽  
Masahiro Okuda ◽  
Hidehiko Suzuki
Keyword(s):  
Spatial Scales ◽  
Lower Atmosphere ◽  
Horizontal Wind ◽  
Leeward Side ◽  
Mountainous Areas ◽  
Wind Fields ◽  
Mountain Waves ◽  
The World ◽  
Geostationary Meteorological Satellite ◽  
Good Proxy

Abstract Imaging observations of OH airglow were conducted at Meiji University, Japan (IN, mE), from May 2018 to December 2019. Mountainous areas, including Mt. Fuji, are located to the west of the imager, and westerly winds are dominant in the lower atmosphere throughout the year. Mountain waves (MWs) are generated on the leeward sides of mountains and occasionally propagate to the upper atmosphere. However, during the observation period (about 1 year and 8 months), only four possible MW events were identified. Based on previous reports, this incidence is considerably lower than expected. There are two possible reasons for the low incidence of MW events: (1) The frequency of MW excitation is small in the lower layers of the atmosphere, and/or (2) MWs do not propagate easily to the upper mesosphere due to background wind conditions. This study verified the likelihood of the former case. Under over-mountain airflow conditions, wavy clouds are often generated on the leeward side. Since over-mountain airflow is essential for the excitation of MWs, the frequency of wavy clouds in the lower atmosphere can be regarded as a measure of the occurrence of MWs. The frequency and spatial distribution of MWs around Japan were investigated by detecting the wavy clouds from color images taken by the Himawari-8 geostationary meteorological satellite (GSM-8) for one year in 2018. The wavy clouds were detected on more than 70 days a year around the Tohoku region, but just 20 days a year around Mt. Fuji. This suggests that few MWs are generated around Mt. Fuji. The differences between these two regions were examined focusing on the relationship between the local topography and dominant horizontal wind fields in the lower atmosphere. Specifically, the findings showed that the angle between the dominant horizontal wind direction and the orientation of the mountain ridge is a good proxy of the occurrence of wavy clouds, i.e., excitation of MWs in mountainous areas. We have also applied this proxy to topography in other areas of the world to investigate areas where MWs would be occurring frequently. Finally, we discuss the likelihood of "MW hotspots" at various spatial scales in the world.

scholarly journals Frequency variations of gravity waves interacting with a time-varying tide

2013 ◽  
Vol 31 (10) ◽  
pp. 1731-1743 ◽  
Author(s):  
C. M. Huang ◽  
S. D. Zhang ◽  
F. Yi ◽  
K. M. Huang ◽  
Y. H. Zhang ◽  
...  
Keyword(s):  
Gravity Waves ◽  
High Frequency ◽  
Lower Atmosphere ◽  
Horizontal Wind ◽  
Frequency Variation ◽  
Time Varying ◽  
Transient Nature ◽  
Critical Layers ◽  
Favorable Conditions ◽  
Frequency Variations

Abstract. Using a nonlinear, 2-D time-dependent numerical model, we simulate the propagation of gravity waves (GWs) in a time-varying tide. Our simulations show that when a GW packet propagates in a time-varying tidal-wind environment, not only its intrinsic frequency but also its ground-based frequency would change significantly. The tidal horizontal-wind acceleration dominates the GW frequency variation. Positive (negative) accelerations induce frequency increases (decreases) with time. More interestingly, tidal-wind acceleration near the critical layers always causes the GW frequency to increase, which may partially explain the observations that high-frequency GW components are more dominant in the middle and upper atmosphere than in the lower atmosphere. The combination of the increased ground-based frequency of propagating GWs in a time-varying tidal-wind field and the transient nature of the critical layer induced by a time-varying tidal zonal wind creates favorable conditions for GWs to penetrate their originally expected critical layers. Consequently, GWs have an impact on the background atmosphere at much higher altitudes than expected, which indicates that the dynamical effects of tidal–GW interactions are more complicated than usually taken into account by GW parameterizations in global models.

scholarly journals Doppler wind lidar activities at Cabauw

2021 ◽  
Author(s):  
Steven Knoop ◽  
Fred Bosveld ◽  
Marijn de Haij ◽  
Arnoud Apituley
Keyword(s):  
Wind Speed ◽  
Wind Profile ◽  
Continuous Wave ◽  
Wind Farms ◽  
Data Availability ◽  
Horizontal Wind ◽  
Horizontal Wind Speed ◽  
Low Clouds ◽  
Wind Measurements ◽  
Wind Lidar

<p>Atmospheric motion and turbulence are essential parameters for weather and topics related to air quality. Therefore, wind profile measurements play an important role in atmospheric research and meteorology. One source of wind profile data are Doppler wind lidars, which are laser-based remote sensing instruments that measure wind speed and wind direction up to a few hundred meters or even a few kilometers. Commercial wind lidars use the laser wavelength of 1.5 µm and therefore backscatter is mainly from aerosols while clear air backscatter is minimal, limiting the range to the boundary layer typically.</p><p>We have carried out a two-year intercomparison of the ZephIR 300M (ZX Lidars) short-range wind lidar and tall mast wind measurements at Cabauw [1]. We have focused on the (height-dependent) data availability of the wind lidar under various meteorological conditions and the data quality through a comparison with in situ wind measurements at several levels in the 213m tall meteorological mast. We have found an overall availability of quality-controlled wind lidar data of 97% to 98 %, where the missing part is mainly due to precipitation events exceeding 1 mm/h or fog or low clouds below 100 m. The mean bias in the horizontal wind speed is within 0.1 m/s with a high correlation between the mast and wind lidar measurements, although under some specific conditions (very high wind speed, fog or low clouds) larger deviations are observed. This instrument is being deployed within North Sea wind farms.</p><p>Recently, a scanning long-range wind lidar Windcube 200S (Leosphere/Vaisala) has been installed at Cabauw, as part of the Ruisdael Observatory program [2]. The scanning Doppler wind lidars will provide detailed measurements of the wind field, aerosols and clouds around the Cabauw site, in coordination with other instruments, such as the cloud radar.</p><p>[1] Knoop, S., Bosveld, F. C., de Haij, M. J., and Apituley, A.: A 2-year intercomparison of continuous-wave focusing wind lidar and tall mast wind measurements at Cabauw, Atmos. Meas. Tech., 14, 2219–2235, 2021</p><p>[2] https://ruisdael-observatory.nl/</p>

scholarly journals Comparison of Large Eddy Simulations of a convective boundary layer with wind LIDAR measurements

2012 ◽  
Vol 8 (1) ◽  
pp. 83-86 ◽  
Author(s):  
J. G. Pedersen ◽  
M. Kelly ◽  
S.-E. Gryning ◽  
R. Floors ◽  
E. Batchvarova ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Geostrophic Wind ◽  
Large Eddy Simulations ◽  
Horizontal Wind ◽  
Convective Boundary ◽  
Horizontal Wind Speed ◽  
Large Eddy ◽  
Lidar Measurements ◽  
Wind Lidar

Abstract. Vertical profiles of the horizontal wind speed and of the standard deviation of vertical wind speed from Large Eddy Simulations of a convective atmospheric boundary layer are compared to wind LIDAR measurements up to 1400 m. Fair agreement regarding both types of profiles is observed only when the simulated flow is driven by a both time- and height-dependent geostrophic wind and a time-dependent surface heat flux. This underlines the importance of mesoscale effects when the flow above the atmospheric surface layer is simulated with a computational fluid dynamics model.

scholarly journals Simulation study for the Stratospheric Inferred Winds (SIW) sub-millimeter limb sounder

2018 ◽  
Author(s):  
Philippe Baron ◽  
Donal Murtagh ◽  
Patrick Eriksson ◽  
Jana Mendrok ◽  
Satoshi Ochiai ◽  
...  
Keyword(s):  
Simulation Study ◽  
Spectral Band ◽  
Chemical Species ◽  
Field Of View ◽  
Emission Lines ◽  
Horizontal Wind ◽  
Line Of Sight ◽  
Heterodyne Receiver ◽  
Vertical Field ◽  
Wind Measurements

Abstract. Stratospheric Inferred Winds (SIW) is a Swedish mini sub-millimeter limb sounder selected for the 2nd InnoSat platform launch planned near 2022. It is intended to fill the altitude gap between 30–70 km in atmospheric wind measurements and also aims at pursuing the limb observations of temperature and key atmospheric constituents between 10–90 km when current satellite missions are probably stopped. Line-of-sight winds are retrieved from the Doppler shift of the emission lines introduced by 5 the wind field. Observations will be performed with two antennas pointing toward the limb with perpendicular directions to reconstruct the 2-D horizontal wind vector. Each antenna has a vertical field of view of 5 km. The chosen spectral band near 655 GHz contains a dense group of strong O3 lines suitable for exploiting the small wind information in stratospheric spectra. Using both sidebands of the heterodyne receiver, a large number of chemical species will be measured including O3-isopotologues, H2O, HDO, HCl, ClO, N2O, HNO3, NO, NO2, HCN, CH3CN and HO2. This paper presents the simulation study for assessing the measurement performances. The line-of-sight winds are retrieved between 30–90 km with the best sensitivity between 35–70 km where the precision (1-sigma) is 5–10 m s−1 for a single scan. Similar performances can be obtained during day and night conditions except in the lower mesosphere where the photo-dissociation of O3 in day-time reduces the sensitivity by 50 % near 70 km. Profiles of O3, H2O and temperature are retrieved with a high precision up to 50 km (

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